Plenty of ground still to cover
GroundCover™ Issue: 58
One of the world"s leading experts in no-till systems says Australian no-till farmers have a long way to go to make the system work as it should. Emma Leonard reports
Ask international no-till specialist Rolf Derpsch to define no-till and he is unequivocal: it is a seeding system with full stubble retention all-year-round, and with as little soil disturbance as possible.
And despite the fact that most no-till farmers in Australia use tine implements, Mr Derpsch says true notill needs disc seeding machines.
The Brazil-based Mr Derpsch acknowledges there has been a significant uptake of no-till with tines in Australia, with productivity benefits, but says Australian growers have a long way to go for the system here to be sustainable.
[Photo (left) by Emma Leonard: SANTFA"s Dr Rohan Rainbow (left) and WANTFA"s Neil Young (right) discuss cover cropping and the use of disc seeders with international no-till specialist Rolf Derpsch]
In recent visits initiated by the Western Australian No-Till Farming Association (WANTFA), and supported by the GRDC Visiting Fellows Program and the Australian Government"s National Landcare Sustainable Industries Initiative, Mr Derpsch has been working with no-till and conservation farming organisations in Australia, especially WANTFA, to help them adopt full stubble retention using disc seeders.
He says tines still create enough soil disturbance to cause stubble incorporation and increased weed germination. This is why there has been an increased reliance on herbicides, and the onset of herbicide resistance.
"No-tillage systems using tines seem to have reached a plateau. To move to the next phase in no-till, Australian farmers need to take a more holistic approach to weed and nutrient management using diverse crop rotations, cover crops, and full stubbleretention systems with disc seeders."
Rolf Derpsch is a passionate advocate of cover cropping and full residue retention. He says this is because almost all the benefits of no-till come from the permanent, complete cover of the soil, rather than the actual no-tilling.
Under his guidance WANTFA, South Australian No-Till Farmers Association and other groups across Australia are experimenting with different cover crops, one of them being Saia oats (Avena strigosa). These oat crops are being grown as a green manure crop. When the crop reaches soft dough stage it is rolled using a knife roller that flattens oats on the soil surface. The knife roller, very similar to a horizontal stone roller, crimps rather than cuts through the stem, so sprouting does not occur.
In Australia, up to five-to-six tonnes of dry matter per hectare (t/ha)per year is left as a thick mat on the soil surface. In South America this can be as high as 12t/ha a year. Also, in South America this decomposes much faster, due to the combination of high temperatures and moisture.
The mat of Saia oats has several benefits:
It breaks down slowly over several years. Sowing a legume crop after the oats ensures there is enough nitrogen in the soil to help soil organisms break down the residues.
"In South America, where summer and winter crops are grown, a cover crop may be grown as often as every two years, to help maintain this weed-smothering stubble mat," says Mr Derpsch.
In Australia, WANTFA is assessing the viable frequency of cover cropping in terms of weed control and overall profitability.
Another part of the trials is assessing disc seeders under a range of Australian conditions. It will assess a commonly-used disc system developed in Brazil and Argentina, which copes well with high residue levels. This system consists of a bigger leading disc, about 40.5 centimetres in diameter, together with a smaller following disc, about 35.5cm in diameter, that is sometimes offset. The discs rotate at different speeds, creating an efficient self-cleaning action.
This system penetrates hard clay soils better than double discs, but they do a poorer job in closing the furrow than double discs the same size, requiring devices to close the furrow and firm the soil behind the discs.
Farmers in WA who are using disc seeders report only minor blockages, hairpinning and some crop emergence problems when seeding into the Saia oat or into a mat of residues from the previous year.
Mr Derpsch also emphasises that no-till does not mean the exclusion of livestock. However, he says it is vital that the hooves of grazing animals only make contact with the residue mat and never the bare soil.
NSW"s Central West Conservation Farming Association is experimenting with full no-till in a mixed farming system as part of its Grain and Graze program. To maintain 100 per cent cover, they are disc seeding into native grasses, which are grazed carefully to ensure permanent soil cover.
Those who have already reduced cultivation and use no-tillage with tines know that changes do not occur immediately but evolve over time.
Mr Derpsch believes that now is the time for Australian growers to take the next steps towards reaping the full benefits of no-till by increasing residue retention and soil cover, and by using disc seeding systems to minimise soil disturbance. He says that from his experience, if Australian farmers continue to use tine systems for seeding, they will never be able to successfully seed into heavy residues.
By Professor João Carlos de Moraes sá, University of Ponta Grossa, Brazil
(Full stubble retention permanent no-till system)
In the initial phase (0-to-five years) the soil starts rebuilding aggregates and measurable changes in the carbon content of the soil are not expected. Crop residues are low and nitrogen needs to be added.
In the transition phase (five-to-10 years) an increase in soil density is observed. The amount of crop residues as well as carbon and phosphorus content start to increase.
In the consolidation phase (10-to-20 years) higher amounts of crop residues as well as higher carbon contents are achieved, a higher cation exchange capacity and water-holding capacity is measured. Greater nutrient cycling is observed.
It is only in the maintenance phase (> 20 years) that the ideal situation with the maximum benefits for the soil is achieved and less fertiliser is needed.
Any tillage performed in phases two to four means a return to the initial phase. Farmers practising a no-till system without full stubble retention, that is, grazing, baling and/or selling residues and/or burning residues, are unlikely to ever leave the initial phase.
It is estimated that farmers using a tine seeding system, even when practising no-tillage with full stubble retention, will only reach the transition phase.
Practising adequate crop rotations and using green manure cover crops once in a while will help reach the maintenance phase.
Region North, South, West